Miserere mei, Deus, secundum magnam misericordiam tuam. (Have mercy on me, O God, after thy great goodness.)
Gregorio Allegri, a 17th century composer and priest, is most well-known for his Miserere mei, Deus, a choral setting of Psalm 51. For several hundred years, Miserere was only permitted to be performed in the Sistine Chapel during Holy Week, the week leading up to Easter. A mysterious and beautiful composition, several composers tried and failed to transcribe the piece. Today, the ban has been lifted and many choirs around the world have performed Miserere.
Psalm 51 is most recognized as the lament penned by David after his affair with Bathsheba and murder of her husband. Have mercy on me, O God… cleanse me from my sin… create in me a pure heart… restore to me the joy of your salvation.